Fibrilating fibrous pulp stock in a gas stream

ABSTRACT

Pulp stock in the form of dehydrated pulp flakes having a moisture content of between 20 and 50 percent is entrained in an airstream and is fed into a fibrilator where it is subjected to a three-dimensional turbulent flow resulting from the unidirectional propulsive force of the airstream and centrifugal force caused by rotating blades within the fibrilator. The flakes impinge upon one another and when disintegrated are withdrawn from the fibrilator by the unidirectional force of the airstream. The less fully disintegrated flakes undergo mechanical impact with a toothed surface in the fibrilator and are then withdrawn. The temperature of the airstream may be controlled by a heat exchanger and the moisture content thereof by valved water and steampipes connected to the airstream carrying duct upstream of the fibrilator.

United States Patent Mekata et a1.

[54] FIBRILATING FIBROUS PULP STOCK IN A GAS STREAM [72] lnventors: Telzo Mekata, 3474, Showa-dori', Takashi Yoda; Masaharu Shiraishi, both of 579/41 Ishizaka, all of Yoshiwara, Shizuokaken, Japan [22] Filed: Dec. 10, 1969 [21] Appl. No.: 883,947

Related US. Application Data [63] Continuation-impart of Ser. No. 598,407, Dec. 1,

1966, abandoned.

[30] Foreign Application Priority Data June 18, 1966 Japan ..41/39219 [56] References Cited UNITED STATES PATENTS 295,617 3/1884 Chichester ..241/40 1 1 Feb. 22, 1972 Primary Examiner-S. Leon Bashore Assistant Examiner-R. l-l. Tushin Attorney-Waters, Roditi, Schwartz & Nissen ABSIRACT Pulp stock in the form of dehydrated pulp flakes having a moisture content of between 20 and 50 percent is entrained in an airstream and is fed into a fibrilator where it is subjected to a three-dimensional turbulent flow resulting from the unidirectional propulsive force of the airstream and centrifugal force caused by rotating blades within the fibrilator. The flakes impinge upon one another and when disintegrated are withdrawn from the fibrilator by the unidirectional force of the airstream. The less fully disintegrated flakes undergo mechanical impact with a toothed surface in the fibrilator and are then withdrawn. The temperature of the airstream may be controlled by a heat exchanger and the moisture content thereof by valved water and steampipes connected to the airstream carrying duct upstream of the fibrilator.

11 Claims, 4 Drawing Figures FIBR'ILATING FIBROUS PULP STOCK IN A GAS STREAM This is a continuation-in-part application of U.S. Pat. application Ser. No. 598,407 filed Dec. 1, l966 and now abancloned.

The present invention is concerned, in general, with a papermaking process and, in particular, with improvements in the method and apparatus for the treatment of a pulp stock with high consistency to suit the production of quality paper with sufficient adaptability to printing.

It is the ordinary practice in the papermaking industry to have a pulp stock subjected to a treatment known as beating after the pulp stock has been passed through the cooking and bleaching processes. The pulp stock thus subjected to the heating process is then disintegrated into small quantities so that the fibers constituting a major portion of the pulp stock are separated from one another, shortened and bruised. In this beating process of a pulp stock, as is well known, the concentration of the pulp stock is one of the most important factors to increase the performance efficiency and to reduce the production cost. Thus, having available an improved method and apparatus adapted to treat a pulp stock with as high a concentration as possible, say, of the order of 50 percent, has doubtlessly been a matter of great consequence to the industry.

In the pulp refiners which have thus far seen wide service in the treatment of a pulp stock, it is required to have the pulp stock diluted in a liquid phase before the pulp stock is subjected to beating. As a consequence, the concentration of the pulp stock is usually limited to about 20 percent. This concentration of the pulp stock could be increased to a certain extent, say, percent or so, provided suitable modifications are made to the method and apparatus used. As long as, however, the necessity of having the pulp stock diluted prior to the beating process is maintained, it will be practically impossible to treat a pulp stock with a concentration far higher than percent without critically impairing the pulp fibers contained in the pulp stock.

In the beating process of the pulp stock, the pulp stock is usually disintegrated into small quantities as it is repeatedly thrown against a serrated wall or passed between relatively moving serrated walls under the influence of a unidirectional and/or rotational force. The pulp stock is, in this manner, subjected to a direct mechanical impact with the serrations so that the fibers in the pulp stock more or less undergo a shearing action due to the so-called knife-edge effect of the serrations. As the consequence, a individual pulp fibers contained in the pulp stock are sheared and torn apart finely so that the final product, or paper, produced from such pulp stock lacks the viscosity required to provide for adaptability to printing. It will be, in this instance, self-explanatory that the shearing action exercised on the individual pulp fibers may be reduced if the concentration of the pulp stock forced to impinge upon the serrated wall is decreased. This is why the pulp stock should be diluted before it is subjected to beating. If, therefore, a pulp stock with a concentration as high as 50 percent or so is fibrilated in the method and apparatus of prior art type, the fibers in the pulp stock would be almost pulverized and consequently the paper or paper product produced from such pulp stock would be crucially void of the viscosity required of quality printing. 7

The present invention, therefore, contemplate'selimination of these and other drawbacks that are inherent in the conventional method and apparatus for fibrilating a pulp stock and it is an important object of the invention to provide a new and improved method-and apparatus adapted for fibrilating a pulp stock for use in the production of paper having adaptability in v printing.

It is another important object of the invention to provide a new and improved method and apparatus for fibrilating a pulp stock with significantly increased performance efficiency and reduced production cost.

It is still another object of the invention to provide a new and improved method and apparatus for fibrilating a pulp stock with a high concentration without impairing the quality of the pulp fibers contained in the pulp stock.

It is still another important object of the invention to provide an improved method and apparatus for fibrilating a pulp stock with a concentration between 20 to 50 percent without imparting a direct mechanical impact, or shearing action, to the pulp fibers in the pulp stock while the pulp stock is being disintegrated into small quantities. 7

It is still another important object of the invention to provide a method and apparatus for fibrilating a pulp stock without need of diluting the pulp stock in a liquid phase prior to the fibrilation thereof.

In order to accomplish these objects of the invention, it is herein proposed to use a pulp stock in the form of substantially dehydrated flakes. The dry pulp flakes are suspended in an atmosphere to which a combined unidirectional and rotational force is imparted. A turbulent flow is thus induced in the suspension of the pulp flakes with the result that the pulp fibers contained in the pulp flakes are twisted and defibered without being subjected to a direct mechanical shearing action or knife-edge effect. A major portion of the pulp flakes is disintegrated, or fibrilated, into small quantities in this manner and is then withdrawn from the turbulent field. The remaining portion of the pulp flakes which is not fully disintegrated is, because of its relatively great weight, urged to approach a toothed surface under the influence of the centrifugal action resulting from the rotational component of the combined force applied thereto. The pulp flakes are then forced against the toothed surface and, as soon as they are disintegrated, the disintegrated portion is immediately withdrawn from the toothed surface under the influence of the unidirectional propulsive component of the force in the turbulent flow. The pulp flakes are thus permitted to stay in the turbulent flow for only a limited period of time and, as a consequence, the pulp fibers contained therein are subjected to a minimum of shearing action by the toothed surface. The result is that the viscosity of the final paper is by no means impaired in the process of fibrilation of the pulp stock and accordingly the paper produced in this manner is specially suited for the purpose of quality printing.

The objects and advantages of the method and apparatus according to the present invention will become more apparent from the following description taken in conjunction of the accompanying drawings, in which:

FIG. 1 is a schematic diagram showing the general construction arrangements of a preferred embodiment of an apparatus adapted for carrying out the method according to the invention;

FIG. 2 is a vertical sectional view of a pulp-feeding means used in the apparatus shown in FIG. 1;

FIG. 3 is a longitudinal sectional view of a fibrilating means used in the apparatus shown in FIG. I; and

FIG. 4 is a section taken on line 1-1 ofFIG. 3.

It is the usual practice in the art that the pulp stock at the drying stage of the pulp-making process is dehydrated mechanically normally up to 55 percent or even up to 60 percent at a maximum by means of a press machine or centrifugal separator without sacrifice to the quality of the fibers in the pulp stock. The moisture remaining in the pulp stock thus dehydrated is deposited in the open cells or interstices of the fibers so as to maintain a swollen, flexible state of the pulp stock. The pulp stock in this state can be most advantageously utilized in the treatment according to the invention, because there is no need of dehydrating the pulp stock for a second time to carry out the method of the invention. The existence of the residual moisture deposit in the fibers in the pulp stock, moreover, is advantageous for the mutual impingement and torsion of the individual fibers placed under the influence of a turbulent flow in the course of the fibrillation. If, in this instance, the pulp stock were to be dehydrated into a sheet form with its moisture content of less than 20 percent, the pulp fibers in the pulp stock, if treated in accordance with the invention, would be finely torn apart or otherwise critically damaged due to lack of flexibility in them.

The pulp stock thus dehydrated to a concentration range from 20 to 50 percent is then crushed-into the form of flakes by the use of a shredder or other suitable means.

According to the invention, the pulp flakes obtained in this manner are then entrained in an atmosphere in which a threedimensional turbulent flow is established. This three-dimensional turbulent flow is built up by a unidirectional propulsive force and a separate rotational force superposed on the former force. The unidirectional force may be obtained by a stream of compressed air with a pressure ranging preferably from 0.4 to 1.5 kg./cm. while the rotational force may be obtained by a suitable rotary member rotating preferably at the speed of 3,000 to 6,000 rpm. The pulp flakes thus placed in such three-dimensional turbulent flow are disintegrated as they impinge upon one another, during which time the pulp fibers in the pulp flakes are subjected to violent torsional stresses and are thereby separated from one another. The disintegrated portion of the pulp flakes is compulsorily withdrawn from the turbulent flow under the influence of the unidirectional propulsive force applied thereto. This is because of the fact that, as the pulp flakes are reduced to small particles, they become less responsive to the centrifugal action due to the reduced weight of the individual particles. The remaining portion of the pulp flakes which are not fully disintegrated into small particles is gradually carried outwardly under the influence of the centrifugal action until the pulp flakes strike against a toothed surface surrounding the pulp flakes. The pulp flakes thus forced against the toothed surface are subjected to mechanical impacts thereupon and are thereby comminuted into small quantities. As the pulp flakes are comminuted, or fibrilated, through impacts upon the toothed surface, they become less responsive to the centrifugal action because of the reduced weights of the small particles disintegrated from the pulp flakes and are withdrawn from the toothed surface under the influence of the unidirectional propulsive force. The pulp stock staying on the toothed surface for only a limited period of time, the pulp fibers in the pulp flakes undergo a minimum of shearing action by the toothed surface.

If desired, the moisture content of the pulp flakes may be increased or decreased by adjusting the moisture in the airstream in which the pulp flakes are to be entrained, thereby enabling the pulp flakes to impinge upon one another or upon the surrounding toothed surface with regulated violence.

A preferred example of the apparatus adapted to carry out the above described method according to the invention is illustrated in FIG. 1.

As shown, the dehydrated pulp stock in the form of flakes is supplied through a conveyor 10 and feeding means 11. The feeding means 11 is connected on the one hand with a source 12 of air through a duct 13. This source 12 of air, which may actually be a fan, blower, air compressor or any similar device, supplies a continuous stream of air under a pressure ranging preferably from 0.4 to 1.5 kg./cm. The feeding means 11, on the other hand, is connected with a fibrilator 14 through a duct 15, the fibrilator being constructed in a manner to be described later. The pulp flakes fed from the feeding means 11 are entrained in the airstream supplied from the source 12 through the duct 13 and are thereafter introduced into the fibrilator 14 through the duct 15. The pulp flakes fibrilated at and by this fibrilator 14 are then passed to a cyclone or centrifugal separator 16 through a duct 17, where the air entrapped in the fibrilated pulp stock is separated and removed therefrom in usual manner. Designated at 18 is a dissolving vat connected with the cyclone or centrifugal separator 16 and filled with clear or white water supplied from a valved feeding pipe 19. The feeding means 11 and fibrilator 14 are driven by motors 20 and 21 through couplings 20a and 21a, respectively.

If desired, the temperature and moisture content of the airstream to be supplied to the fibrilator 14 through the ducts 13 and 15 may be adjusted. For this purpose, valved air pipe 22, water pipe 23 and steampipe 24 communicating with the water pipe 23 all communicate with the duct 13 through an ejector 25.

If further desired, the pressure of the airstream supplied from the source 12 through the duct 13 and the power load on the motor 21 for the fibrilator 14 may be detected by a control means 26 to regulate the speed of motor 20 for the feeding means 11.

Also, the amount of water to be supplied through the water pipe 23 to the airstream in the duct 13 may be regulated by a control means 27 through detection of the amount of water to be separated and removed from the fibrilated pulp stock at the cyclone or centrifugal separator 16. To control the temperature of the airstream in the duct 13, the amount of air to be supplied through the air pipe 22 and the amount of the steam supplied through the steampipe 24 may be regulated by a control means 28 in accordance with the temperature of water detected at the cyclone or centrifugal separator 16.

The temperature of the airstream supplied from the airstream source 12 may also be changed with use of a suitable heat exchanger 29 combined with the source 12.

The detailed construction of the feeding means 11 is illustrated in FIG. 2.

As shown, the feeding means 11 has a hopper 30 into which the dehydrated pulp flakes are carried by the conveyor 10. The hopper 30 is supported by a generally cylindrical casing 31 with closed ends. The cylindrical casing 31 has journaled in its end walls a rotary shaft 32. The rotary shaft 32 is connected at one end to the drive shaft of the coupling 20a of the motor 20 through one sidewall of the casing and at the other end is supported rotatably on the other sidewall of the casing through bearings (not shown). The shaft 32 is provided radially with a plurality of blades 33. The cylindrical casing communicates at its top with the hopper and at its bottom with the duct 13 through an outlet 34.

In operation, the rotary shaft 32 is driven from the motor 20 through the coupling 200 so that the blades 33 rotate in the cylindrical casing at a predetermined velocity. Thus, the pulp flakes carried through the hopper 30 are fed into the duct 13 constantly through the outlet 34. The amount of the pulp flakes fed into the duct 13 can be determined by the control means 26 in accordance with the pressure of the airstream in the duct 13 and the power load on the motor 21 for the fibrilator 14, as previously discussed. The pulp flakes are thus entrained in the airstream under pressure in the duct 13 and are then forced into the fibrilator 14 through the duct 15 The fibrilator 14 is constructed as illustrated in FIGS. 3 and 4. As shown, the fibrilator 14 essentially comprises a generally cylindrical casing 35 and a rotor 36 mounted therein. The casing 35 communicates through one end wall thereof with the duct 15 and through the other end wall with the duct 17. The cylindrical casing 35 is provided on the internal peripheral wall thereof with a metallic lining 37. The metallic lining 37 is finely toothed over its surface 37a extending halfway from the upstream end wall and merges with an arcuately curved wall surface 3711 which terminates at the upstream end of the duct 17, as clearly seen in FIG. 3. The curved wall surface 37b may preferably curved approximately at 45 to the internal surface of the cylindrical casing 35 thereby to avoid formation of a dead pocket.

The rotor 36 is supported on a rotary shaft 38 through end walls 39 and 40 and the rotary shaft 38, in turn, is supported rotatably on the walls of the ducts 15 and 17 through bearings 41 and 41' and packings 42 and 42', respectively.

The rotary shaft 38 is connected at one end with and driven by the coupling 21a of the motor 21. The end wall 39 has formed centrally therein a bore 43 to receive the leading end of the duct 15. On the sidewalls 39 and 40 of the rotor 36 are radially supported a plurality of blades 44, as clearly seen in FIG. 4.

In operation, the rotor 36 is rotated by the motor 21 through the coupling 21a and revolution shaft 38. The revolution speed of the rotor 36 may range from about 3,000 to about 6,000 rpm, which may correspond to the circumferential speed of about 60 to meters per second of the rotor 36. A field of constant centrifugal force is thus created about the axis of the rotation of the rotor 36 through revolution thereabout of the blades 44 of the rotor 36.

The centrifugal force thus established in the casing 35 is acted upon by a second, unidirectional force which is built up substantially in the direction parallel to the axis of rotation of the rotor 36, namely, perpendicular to the centrifugal force, by a constant rapid stream of air supplied from the source 12 of the airstream by way of the ducts l3 and 15. This unidirectional force may be about 0.4 to 1.5 kg./cm. The unidirectional force being combined in superposed relationship with the centrifugal force, a violent turbulent flow in a gaseous phase is established in the casing 35.

The unidirectional stream of air, as it is passed from the duct 13 to the duct 15 at the bottom of the feeding means 11, carries thereon a regulated amount of dehydrated pulp flakes supplied constantly through the opening 34 in the feeding means 11. The pulp flakes thus carried in the airstream is forced to gush into the casing 35 through the duct 15 and are then subjected to the violent turbulent flow as they stay in the casing 35 of the fibrilator 14.

The individual pulp flakes so introduced into the casing 35 of the fibrilator 14 are caused to rub and impinge upon one another and, as a result, are disintegrated into small quantities. The pulp fibers contained in the pulp flakes are, as the pulp flakes are comminuted, subjected to torsional and frictional forces and are thereby loosened from one another. The portion of the pulp flakes rendered into small quantities with reduced weight in this manner is less responsive to the centrifugal action because of the very reduced weights thereof and is moved downstream under the influence of the unidirectional propulsive force until they are discharged out of the fibrilator 14 by way of the duct 17. The remaining portion of the pulp flakes, which are not fully disintegrated at this stage, are urged to approach the toothed surface 37a of the lining 37 due to the centrifugal action exerted by the blades 44 of the rotating rotor 36. The pulp flakes then are subjected to mechanical impacts as they are forced against the toothed surface 37a. The pulp flakes staying on the toothed surface-37a are thus subjected repeatedly to the disintegrating action as the bladed rotor 36 rotates and are thereby reduced to small quantities. As the pulp flakes are disintegrated in this manner, the pulp fibers contained therein are also subjected to torsional and frictional forces as the pulp flakes impinge upon one another and upon the toothed surface 37. Since, at this moment, the individual particles of the disintegrated pulp flakes are sufficiently lighter in weight than the pulp flakes in the initial state, they are less subject to the centrifugal action andconsequently are forced out of the casing 35 of the fibrilator 14 by the action of the unidirectional propulsive force. Although, in this instance, a portion of the pulp flakes is subjected to a direct mechanical impact with the toothed surface, the pulp fibers in the pulp flakes are exposed to only a minimum of shearing action by the teeth on the toothed surface because the pulp flakes are withdrawn from the surface as soon as they are disintegrated into small quantities with reduced weights.

Thus, it will be understood that the pulp flakes can be fibrilated without destroying the cellulosic system of the fibers contained therein according to the invention. This has been ascertained by m icr os copic examinations congtedbm inventors, the results of which, however, are not herein presented.

If desired, the time period for which the pulp flakes are permitted to stay in the fibrilator 14, which time period governs significantly the quality of the disintegrated pulp flakes, may be adjusted by regulating the velocity of the airstream supplied from the blower or air compressor 12 and/or the rate of feed of the pulp flakes supplied through the feeding means 11 by the adjustment of the load on the motor 20, as desired.

it may be mentioned that the pulp flakes are proportionately more responsive to the centrifugal action in the fibrilator 14 if they contain more moisture. For this reason, it will be desirable to adjust the moisture content of the air to be admixed to the pulp flakes by regulating the amounts of air,

15 water and hot steam supplied through the valved pipes 22, 23,

and 24, respectively.

It may also be mentioned that the pulp flakes supplied from the conveyor 10 may be bypassed around the feeding means 11 and introduced directly into the fibrilator 14 depending 0 Q upon the intended type of the finished paper or paper product.

In such instance, it will be advantageous to have the airstream source 12 located in the vicinity of the outlet of the duct. 'Where, moreover, a blower or fan is used as the airstream source 12, the fan or blower may be so arranged as to rotate 5 f concentrically with the revolution shaft 38 of the fibrilator 14.

The advantages of the method, and the apparatus to be used therefor as well, will be better understood from the following examples.

EXAMPLE 1 The flakes of unbleached pulp of percent concentration i were fed to the feeding means 11 with its bladed shaft 32 rotating at the speed of 300 r.p.m. These pulp flakes were then introduced into an airstream supplied from the blower 12 with 40 defibered in the fibrilator 14 were passed to the vat 18 filled with white water via the cyclone 16 to obtain a pulp stock of 5 percent concentration. This pulp stock was made into paper at l a predetermined beating rate by a process in compliance with the TAP?! Standards. Tests were conducted on the resultant paper for strength at 20 C. temperature and 65 percent relative humidity and the results of the tests were compared with 5 those conducted on a paper produced from a usual beat pulp ;prepared as a starting pulp material of 5 percent concentral tion.

5O; While there was observed no appreciable difference in the l specific bursting strength and breaking length, the paper I produced by the method according to the invention was considered to far excel] the conventionally beat paper especially 1 in respect to the tearing strength and elongation. This is shown in Table 1, wherein the paper produced by the method acf cording to the invention is referred to as A" and the paper produced from the conventional pulp stock with low concentration as B (such denotation applies to all the Tables that is stsie lqflonn j.

Norm-A: lnper processed from a starting pulp oi 20% concentration according to the invention; B: Paper processed from the conventional low concentration bent pnlp.

. gards the specific bursting strength and breaking length. The

paper produced with use of a pulp stock prepared in the method according to the invention, however, showed nearly EXAMPLE 4 The process adopted in Example 1 was followed, except that pulp flakes of 40 concentration were used. The results of tests conducted on the paper produced from the pulp stock thus fibrilated are indicated in Table 4, from which it will be observed that, while no appreciable improvement is achieved over the conventionally produced paper especially in respect to the specific bursting strength and breaking length, the paper obtained in this example is recognized to have a re- 100 percent greater specific tearing strength and elongation. 1O markably greater specific tearing strength and elongation,

This is clearly seen in Table 2. W

granting that the breaking length, in particular, is rather lower than that of the paper prepared with use of the pulp flakes of 30 concentration as in Example TABLE 2 Beating Breaking Specific time Freeness Bursting length Elongation tearing (min) (00.) strength (km.) (percent) strength A 43 5. 36 6. 40 2.9 230 B 10 620 5. 30 6. 35 4. 365 23.25 98.88 99.22 137.93 158.70 60 5.80 7.58 3.4 240 485 5. 78 7. 66 3. 9 267 25.00 99.66 101.6 114.7 111.25 A 70 6. 0 8. 16 3. 4 203 B 22 390 6. 0 8. 37 3. 7 281 B/A 31. 43 100. 33 102. 57 108. 82 138. 43 75 6.66 8.0 3.3 168 30 290 6. 67 8. 3. 8 237 B/A 40. 0O 100. 15 102. 60 115. 15 141. 67

No'rE.A: Paper processed from a starting pulp of concentration according to the invention; 13: Paper processed from the conventional concentration beat pulp.

TABLE 4 Beating Breaking Specific time Freeness Bursting length Elongation tearing (min.) (cc.) strength (km.) (percent) strength A 43 5. 36 6. 40 2. 0 230 B 17 620 5. 6. 4. 0 310 39. 53 98. 88 100. 00 137. 93 138. 70 60 5. 80 7. 58 3. 4 240 30 485 5. 75 7. 3. 7 363 50. 0 99. 14 98. 04 108. 82 151. 25 70 6. 05 8.16 3. 4 203 40 390 6. 00 8. l3 3. 0 330 57. 14 99. 17 99. 63 114. 71 162. 56 75 6.66 8.07 3. 3 168 52 200 6. 60 8.00 1. 2 253 69.33 09.10 09.13 127.27 150.60

Norm-A:

Paper processed from a starting pulp of 20% concentration according to the EXAMPLE 3 Pulp flakes of 30 percent concentration were processed in a manner similar to that used in Example 2 and were recycled from the cyclone 16 back to the conveyor 10 for reprocessing in the feeding means 11 and fibrilator 14. This recycling of the once fibrilated pulp stock was intended to see if it would provide better results than obtainable by the single cycling of the pulp stock. As is observed in Table 3 below, however, the paper produced with use of such reprocessed pulp stock is substantially no different in the various aspects of the paper 1 properties from the paper produced from the pulp stock processed in a single cycling as in Example 2, except only that the time period required for the beating was reduced to a certain extent. Thus, it can be concluded that the recycling of the pulp stock in the fibrilating line is superfluous, only adding to EXAMPLE 5 The process of Example 1 was also followed, except that the concentration of the pulp flakes as a starting material was increased to 50 percent. The results of conducted tests on the resulting paper, as indicated below, reveal that, while the specific bursting strength and breaking length remain comparable to those of the conventional paper, the paper prepared in this example is superior to the conventional paper in respect to the elongation. The specific tearing strength is, however, considered not satisfactory. The tearing strength of the paper obtained in this example may be improved to some extent if the degree of beating is increased.

the number of steps.

TABLE 3 Beating Breaking Specific time Freeness Bursting length Elongation tearing (min) (cc.) strength (km.) (percent) strength 43 5.36 6.40 2.9 230 9 620 5.38 6.42 3. 333 20. 93 100. 37 .100. 31 131. O3 144. 78 60 5. 80 7.58 3. 4 240 14 485 5. 81 7. 60 4. 4 298 23. 33 100. 17 100. 26 120. 41 124. 16 6,05 8.16 8. 4 203 20 800 6. 10 8. B 3. 0 278 28. 57 100. 88 100. 40 114. 7 180. 05 6.06 8.07 8.8 108 ll. 20 200 0.07 8. 25 4. 5 238 ll/A 34.07 100.15 102. 23 130.36 141.67

N0'llC.---AZ lupor processed from a. starting pulp of 20% concentration according to the invention; ll: lnpot' processed from tho eonvontlonul low concentration boat pulp.

TABLE 5 Beating Breaking Specific time Freeness Bursting length Elongation tearing (min (cc.) strength 01m.) (percent) strength NorE.A:

invention; 13: Paper processed from the conventional low concentration beat pulp.

EXAMPLE 6 The process of Example 1 was invariably followed, except that the concentration of the pulp flakes was further increased to 60 percent. As seen from Table 6 below, the paper produced with use of pulp stock with such a high concentration is considerably inferior to the conventional paper at least with respect to the specific tearing strength. As to the elongation property of the paper, however, the paper produced from the pulp stock obtained in this example is superior to that of the conventional paper. As regards the specific bursting strength and breaking length, substantially no difference is observed. it is thus considered from this example that the concentration of the pulp stock should not exceed 60 percent from the view point of economical and operational limitations It should now be understood that the method and apparatus to carry out the method according to the invention are given by way of illustration only and that modifications thereof may be made which are obvious to those skilled in the art without departing the spirit and scope of the present invention as defined in the appended claims.

.force in a predetermined direction, entraining a pulp stock in the form of dehydrated pulp flake in said unidirectional stream to suspend the pulp flakes therein, said pulp stock having a flake moisture concentration between 20 and 50 perin the moisture adjustment of th l required cent, imparting to the suspension of said pulp flakes a centrifu TABLE 6 Beating Breaking Specific time Freeness Bursting length Elongation tearing (min.) (cc.) strength (km.) (percent) strength For the purpose of better understanding of the major properties of the paper produced from the pulp stock prepared by the method according to the invention, the results of tests conducted on the papers as stated in the above examples are tabu-' lated in Table 7 by the pulp stock and in percent ratios to the properties of conventionally prepared paper.

- gal force which is built up by a rotational force having an axis TABLE 7 55 Pulp con- Specific Breaking Elonga- Specific sistency Freeness bursting length tion tearing properties (cc.) strength (km.) (percent) strength 290 99. 10 99. 75 139. 4 178. 6 620 98. 88 99. 22 137. 93 158. 7 307 485 99. 66 160.06 114. 7 111. 25 o 390 100. 33 102. 57 108. 82 138. 43 290 100. 15 102. 60 115. 15 141. 67 Rec 016 620 100. 37 109. 31 131. 03 144. 78 ryoeess 485 100. 17 100. 26 129. 41 124. 16 g 390 100. 83 100. 49 114.70 136. 95

of rotation substantially parallel to said predetermined direction of said propulsive force for thereby establishing a turbulent flow with combined propulsive and centrifugal forces to cause said pulp flakes to impinge upon one another and subject the pulp fibers therein to torsional and frictional forces so as to be separated from one another as the pulp flakes are disintegrated, withdrawing the disintegrated portion of the pulp flakes from said turbulent flow under the influence of said propulsive force, subjecting the remaining portion of the pulp flakes to mechanical impact with a toothed surface under the influence of said centrifugal force until said remaining portion of the pulp flakes is reduced to small quantities and withdrawing these small quantities from said toothed surface under the influence of said propulsive force.

2. A process as set forth in claim 1, wherein said propulsive force is about 0.4 to 1.5 kg./cm.

3. A process as set forth in claim 2, wherein said centrifugal force is built up with a rotational force resulting from a rotation at about 3,000 to 6,000 rpm.

4. A process as set forth in claim 3, comprising adding moisture to said unidirectional stream before the stream carries said pulp flakes.

5. A fibrilator for fibrilating a pulp stock comprising a cylindrical casing with closed ends, a rotatable shaft journaled to said closed ends, a rotor on said shaft, a plurality of radial blades on said rotor, a metallic lining attached to said casing on the inner surface thereof, said lininghaving a toothed surface extending halfway from the upstream end of said casing and merging with an arcuately curved surface terminating at the downstream end of said casing, an inlet duct connected to said casing at said upstream end thereof to pass pulp flakes entrained in a rapid unidirectional stream in a gaseous phase into said casing, an outlet duct connected to said casing at the downstream end thereof for discharging pulp flakes fibrilated in said casing, and a motordriving said rotor via said shaft.

6. Apparatus for fibnlatmg a pulp stock in a gaseous phase,

which apparatus comprises means for conveying a supply of pulp stock in the form of dehydrated pulp flakes, means for supplying a unidirectional stream in a gaseous phase exerting a propulsive force in a predetermined direction, means for feeding said pulp flakes from said conveying means to said unidirectional stream at a regulated rate, a fibrilator including a casing with an inner toothed surface, a rotor mounted on a shaft and rotatable within said casing about an axis of rotation substantially parallel to the said predetermined direction of said propulsive force, means for rotating said shaft, said rotor including a plurality of blades radially mounted thereon for producing centrifugal force in said casing, said fibrilator having an inlet for the introduction of the unidirectional stream with the pulp flakes into the fibrilator, to subject the flakes to a turbulent flow formed by the combination of the propulsive and centrifugal forces in the fibrilator.

7. Apparatus as set forth in claim 6, wherein said means for feeding said pulp flakes comprises a hopper to receive the pulp flakes from said conveying means and a cylindrical casing with closed ends communicating at its top with said hopper and at its bottom with said means for supplying a unidirectional stream through an outlet means.

8. Apparatus as set forth in claim 6, further comprising a valved pipe for supplying air, a valve pipe for supplying water and a valved pipe for supplying hot steam, said pipes all being operatively connected with said means for supplying a unidirectional stream for adjusting the moisture content and temperature of said stream upstream of said means for feeding said pulp flakes.

9. Apparatus as set forth in claim 8, further comprising means for controlling the rate at which said pulp flakes are fed to said unidirectional stream in accordance with the pressure of the gaseous stream.

10. Apparatus as set forth in claim 8, further comprising means operatively coupled with said valved pipe for supplying water to control the amount of water introduced through said valved pipe in accordance with the amount of water removed from the fibrilated pulp stock downstream of said fibrilator. 

2. A process as set forth in claim 1, wherein said propulsive force is about 0.4 to 1.5 kg./cm.2.
 3. A process as set forth in claim 2, wherein said centrifugal force is built up with a rotational force resulting from a rotation at about 3,000 to 6,000 r.p.m.
 4. A process as set forth in claim 3, comprising adding moisture to said unidirectional stream before the stream carries said pulp flakes.
 5. A fibrilator for fibrilating a pulp stock comprising a cylindrical casing with closed ends, a rotatable shaft journaled to said closed ends, a rotor on said shaft, a plurality of radial blades on said rotor, a metallic lining attached to said casing on the inner surface thereof, said lining having a toothed surface extending halfway from the upstream end of said casing and merging with an arcuately curved surface terminating at the downstream end of said casing, an inlet duct connected to said casing at said upstream end thereof to pass pulp flakes entrained in a rapid unidirectional stream in a gaseous phase into said casing, an outlet duct connected to said casing at the downstream end thereof for discharging pulp flakes fibrilated in said casing, and a motor driving said rotor via said shaft.
 6. Apparatus for fibrilating a pulp stock in a gaseous phase, which apparatus comprises means for conveying a supply of pulp stock in the form of dehydrated pulp flakes, means for supplying a unidirectional stream in a gaseous phase exerting a propulsive force in a predetermined direction, means for feeding said pulp flakes from said conveying means to said unidirectional stream at a regulated rate, a fibrilator including a casing with an inner toothed surface, a rotor mounted on a shaft and rotatable within said casing about an axis of rotation substantially parallel to the said predetermined direction of said propulsive force, means for rotating said shaft, said rotor including a plurality of blades radially mounted thereon for producing centrifugal force in said casing, said fibrilator having an inlet for the introduction of the unidirectional stream with the pulp flakes into the fibrilator, to subject the flakes to a turbulent flow formed by the combination of the propulsive and centrifugal forces in the fibrilator.
 7. Apparatus as set forth in claim 6, wherein said means for feeding said pulp flakes comprises a hopper to receive the pulp flakes from said conveying means and a cylindrical casing with closed ends communicating at its top with said hopper and at its bottom with said means for supplying a unidirectional stream through an outlet means.
 8. Apparatus as set forth in claim 6, further comprising a valved pipe for supplying air, a valve pipe for supplying water and a valved pipe for supplying hot steam, said pipes all being operatively connected with said means for supplying a unidirectional stream for adjusting the moisture content and temperature of said stream upstream of said means for feeding said pulp flakes.
 9. Apparatus as set forth in claim 8, further comprising means for controlling the rate at which said pulp flakes are fed to said unidirectional stream in accordance with the pressure of the gaseous stream.
 10. Apparatus as set forth in claim 8, further comprising means operatively coupled with said valved pipe for supplying water to control the amount of water introduced through said valved pipe in accordance with the amount of water removed from the fibrilated pulp stock downstream of said fibrilator.
 11. Apparatus as set forth in claim 6, wherein said means for supplying of unidirectional stream includes a heat exchanger for adjusting the temperature in the said stream in a gaseous phase. 